Electric discharge tube



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UNITEDSTATES* l'rfa'lrl-NT oFF'Icnf GILLEs HoL'sT AND ALBERT DoUwEHs, oE'ErNDHovEN.' NETHERLANDS, AssIeNons To N. v. PHILIPS GLomAHrENEABnIEHEN, 0E EINDHOVEN, NETHERLANDS.

ELECTRIC DISCHARGE TUBE.

Appueeuen 11e-august 25, 1925, serial Ne. 52,398, and' m Netherlands November 17, 1924.

. This invention relates to an improvement .in or modification ofthat described in specif `ication No.' 5,108 concerning electricdischarge tubes, and morel particularly disl charge tubesin which during the operation very high tensions occur as, for example,

tubes for `,Rntgen.therapeutics. j f According to the prior specification mem'- bers of a discharge tube between which during the operation a very highpotential difference occurs, are connected to each other by a wall which consists of parts of insulating material alternating with partsl of conduc'tivev material. By arranging-the parts l5 of conductive material in such a manner that a desired potentialpcan be impressed on them,

it lis -made .possible to divide the` total potential-ditference occurring during the operation in the discharge tube, equally over the 9 0 insulating parts, which o'ers the advantage that the total insulating length of these parts' together canv be materially smaller than the A insulating length of.4 one insulating jpiece would have to be. According to the prior specification the wallwhich connects the' members between which 4during the operation avery high potential vdiierence ocurs,

-` forexample, electrodes of the 'discharge tube, may formv wholly or partly the outer wall of the discharge tube. 1 x l, "U l In discharge tubes .according to theprior Y specification of the latter kind it may happen that undesired discharges, occurhetween the electrodes.- If,' "f or examplethc elec trodes have surfaceslying .close to eachr other so that even when `supplying avery high tension there does not occur any ionization between these' surfaces, it may yet` occurv that between other parts ozf the jelec'# v 40, trodesor aln/g' other paths .undesired Vdischarg are produced. ,'In 'order' to' obtain a suicient insulation along the outer wall,

this wall andthere'fordjalso, the inner roomv u l have d1mensions' which' vare a 'greatr many times larger ythan the distance between .must

` the said surfaces of the electrodes so 4.that discharge paths Of'mterlally larger length i een b-.feeesr which ses .ianiz'etioe may cur." 1 y. y '50. Accordingitofgthe present.v invention,- in

order 'toI obvlate this .disadvantage vconductive wallsare connected'to the conductive l 'Y parts of the outer -wallinsuch a manner that that part 'of the inner room of the discharge tube in which undesired discharges might occur, is divided into a series of discharge paths. L

According to. this invention, the interiory space of the discharge tube is, preferably, dlvided in to a number of compartments .which are bounded not only by the insulating andconductive partsof the outer wall, I

'or by the electrodes, but principally byvpartitions which. areconnectedto successive con-4 ductive parts of the outer wallof the discharge tub'e.

` If hat part of the outer wall which lcomposed of insulating and conductive parts, 'is constituted by an oblongv vessel, the pare '.titions may extend on either side towards lthe -middle oi. said vessel, the free ends of the partitions, preferably, overlapping each other. l y

The present invention may be applied inter alia to X-ray tubes comprising an inoandes'centfcathode. If in this 'case the incandescent cathode is arranged within a metal vesseh which is separated'from'the anticathode by an insulation capable of `resisting the total ol'ierating` voltage, and

vwhich on the anticathode side is narrowed to an aperture forthe passage .of the cathode rays and if that part of the anticathode which is struckv by the cathodeirays, is lo- .cated in or near said. aperture, the anticathode may beconnected accordingv to the present invention to 'aconductive wallv sur` rounding at least partly the lmetal ,vessel in which the incandescent cathode is arranged. Also the anticathode may be connected t0 a- -conductive wall'which surrounds a consid- ,erable portion of the length of the glass tube to the v'end of wl ich the` anticathode is secured., '16..

[According to lthis invention',"the partitions which may extend on either-side tothe middle Aof the X`ray tube, may preferably end in' or near a .plane at right angles to the axis "of the' tube, and i'ntersectingf the metal essel in which-the incandescentcathode is arranged.

ico4

' Whenioperating .discharge 'tlibes according tothe presentf-in'vention thecondctive,

of theouter wall are preferably given4 such potentials that the total, potentialv difference occurring between; 'the electrodes is equally divided over the insulating parts of the outer wall.

The accompanying drawing illustrates, by way of example, an incandescent cathode X- ray tube to` which the invention is applied and also illustrates diagrammatically theinsulation for' operating said tube.

The X-ray tube illustrated vis provided with an anticathode 1 the edge of which isA hermetically sealed to the end of a glass tube 2. The anticathode is hollow in or'der that it may be cooled by a suitable cooling medium supplied by a tube 3 secured in the anticathode. A11 incandescent cathode 4 is arranged in a metal vessel 5 mounted coaxially with the 'anticathode and having on the side of the latter an aperture 6 for the passage, of the cathodeand X-rays. rllhe edge of the metal vessel 5 is hermetically sealed to a glass tube 7 which passes into a conical part 8 in which isprovided a win- 'dow 9 in order to hermetically close the dist charge tube and to allow the X-rays `to pass. One end of the incandescentl cathode 4 is electrically connected to the metal vessel 5 whereas the pole wire supporting the other end of the filament, is .insulated from the metal vesselF by a bead l10 of quartz or 1- hermetically any other insulating material. A leading-in wire 12 for this end of the filament and a leading-in wire 11 which is connected to the metal vessel, pass through tubes 14 and 13 of insulating material, for example, of glass,- in order to prevent the two leading-in wires .from being shortcircuited and from coming into contact with 4The ends of the glass tubes 2 andy 8 are sealed to a cylindrical vessel consisting of metal rings 16,l 17 18. 19 and 20 and of glass parts 21, 22, 23 and 24 which are Ihermetcally sealed to the said metal rings. To the metal rings' 16, 17, 19 and 20 are connected metal partitions 25,- 26, l27 .and 28which extend on either sideto the middle of the X-ray tube. A'cylindrical wall 29 lwhich surrounds the glass tube 2. is connected to the anticathode, an'd a cylindrical metal wall 30 starting fromv the anticathode,

extendsy downwardlyover the metal vessel 5.

When operating the discharge tube, a source of alternatingcurrent is brought via a regulable vresistance 34 Linto connection with a primary winding 35 of a heating current transformer and through a regulable resistance with a primary winding 36 of a high tension transformer byclosing a bipolar switch 33. A secondary winding 37 of the heating current transformer is connected to the incandescent cathode 4 byv means of the leading-in wires 11 and '12 whereas a secondary winding 38 of the high tension transformer is connected at its ends to the anticathode 1 and to the metal vessel 5 and is divided into six equal parts, branches to the metalrings 16-20 being provided so that ference i which the metal walls in the tube.

the total potential difference is equally divided among the insulating parts of the i outer wall of the tube. The middle of the l secondary winding which is connected to the rlng 18, is at the same time in connection with an iron core 39 of the transformer which are drawn to the anticathode where they generate X-rays. Owing to the particular shape of the vessel 5, the electrons can strike only a small surface of the anticathode mirror. The X-rays generated leave the tube through the window 9 and for the other part are absorbed by the metal partitions. By means of the partitions the interior space of the X-ray tube is divided ,into annular compartments A, B, C, D, E and F and a chamber G which 'directly surrounds the two electrodes. The annular chambers A-F are bounded not only by the metal rings 16-20 and by insulating'walls but principally by partitions which are connected to successive rings. Consequently in each compartment there principally occurs the potential difalso occurs between the successive rings. If, for example, in the X-ray tube illustrated the total`operating voltage is 300.000 volts the potential difference `prmciv ally voccurring in eachk compartment will be` ut 50.000 volts so that the possibility that f undesired discharges are produced is considerably 'diminished by providing theparv titions. Near' the open ends-of the compart-` inents B,.C, D and F -en'd each timelpar-A titions which have a higher potential difference relatively to the wallsl of each compartment than the potential difference occurring between the said walls. This offers, however, no diiculty asthe distances between the parts having a higher potential difference are small. It is obvious that in the compartment G there occur very high potential differences .but they cannot have any detrimental influence as the dimensions of this compartment are but small. y The penetration of electrons is further prevented by the fact .thatthe partitions overlap each other.

The partitions offer the incidental advantage that X-rays which do not belong to the active beam, can be absorbed.

The metal rings 16-20 may advantageously be made of chrome 'iron of suitable composition, very well to glass,is not porous and is easily deprived of occluded gases.` For constitutingthe p artitionsfas well as the wall of the f' vessel 5 and the walls 25-3Q'may, preferas this material'can be sealed f ably, be chosen a material which is easily deprived of occluded gases and 'which absorbs X-rays. For example for constituting these walls chrome iron may also be that part ofthe outer wall of the tube which connects electrodes receiving during the operation a high potential difference, consists of'parts of insulating material alternated by parts of cnductive material, characterized in that conductive partitions are connected to the conductive parts of the outer wall in such a manner that that part of the.

divided in a number of compartments which -are boundednot only by the-insulating and conductive parts of the outer wall and some by the electrodes, butl principally by partitions lwhich are connected to successi-Ve conducting parts of the outer wall of the discharge tube.I

Y- 3. A discharge tube according to claim 1,

lcharacterized in that that portion of the outer wall which is composed of insulating and conductive parts, is an oblong vessel, the partitions extending on either side to theV middle of the said vessel.

4. A dischargev tube according to claim 1, characterized' in that that portion of the outer wall which is composed of insulating and conducting parts, is an oblong vessel, the partitions `extendimgf on' either side to the middle of the said vessel, and the free cathode by an vinsulation capable of resisting the .total operatingA Voltage, and which on the side-of the anticathode is narrowed Vto an aperture for the passage of the cathode rays, that part of the antlcatho'de which 1s struck by the cathode'rayrs, beinglccated in orpnear sald aperture', characterized in that t-the anticathode is connected a conv ductive wall which surrounds at least partly the metal vessel in which the lincandescent cathode is arranged.

6. An incandescent cathode X-ray tube,

total operating voltage, and which on the side of 'the' anticathode is narrowedr'to an i tially at right angles to the axis of thegtube aperture for the passage of the cathode rays,

that part of the anticathode which is struck `the end of which the anticathode is secured over a considerable portion of its length.

7. An -incandescent cathode X-ray according to claim 1, in which an incandes" cent cathode is arranged Within a metal vessel which `is separated from the anticathode by an insulation capableV of resisting the to'- tal operating voltage, and which on the side of the anticathode is narrowed to`an aperture for the passage of the cathode rays, that part of the anticathode which is struck by the cathode rays, being located in or near said aperture, characterized in that to the anticathode is connected aconductivewall which surrounds at least partly the metal vessel in which' the incandescent-cathode is arranged, the anticathode and the metal vessel with the aperture for the passage of the cathode raysibeing coaxially arranged, said tube being further characterized in that the partition extending 'on either side toy the middle of the tube and in aplane substan- 05 and cutting the metal vessel in which the incandesc'erit cathode is arranged.

8. yAn installation for operatingy a discharge tube according to claim 1, charactei-ized in that the conductive parts of the outer-wall are given such4 potentials 'that the total potential differencey occurring' be" tween the electrodes, is equally divided over the insulating parts of the outer wall;

9. A discharge tube according to claim 1, 10i characterized in that the interior space is divided intol a number of compartments which are ,bounded not only by the insulating and conducting parts of the outer wall and some by the electrodes, bu/t principally Il. by partitions (which are connected to suc-v cessive conducting parts of the outer wall of. the discharge tube,A and further characterized in that that portion of the outer wall which is composed of"insulating and conlll ductive parts, is an oblong vessel, the partitions extendingon either side to the middle of the said vessel. In testimony whereof We aliix our signatures, at the city of Eindhoven, this 10th day 120 v y GILLES HoLsT.

ALBERT BOUWE Rs. 

